Apparatus for mounting stern rollers in anchor planting tenders

ABSTRACT

An anchoring tender has a centrally indented stern and a center stern member adapted to fit and be pivotally fastened by a forward end in said indented stern for pivoting an after free end downward from an inoperative and non-drag position within said tender. A stern roller is mounted for rotation on said free end of the longitudinal member, the axis of rotation of the stern roller being transverse the indented stern and the stern roller being out of the water when the longitudinal member is in inoperative and non-drag position, and in the water and below center of gravity of tender when transverse member is pivoted downward to an operative position. The perimeter of the stern roller is a continuation of a channelway in said stern member and together define approximately an end of a catenary in a vertical plane formed by an anchor line led out by said tender from a rig to be anchored. Lowering the stern roller below the center of gravity of the tender stabilizes its stern under load of anchoring tackle, and the application of power in approximate line of catenary reduces necessary power by more than half, and diameter of stern roller by half.

United States Patent Korkut [451 Feb. 13, 1975 APPARATUS FOR MOUNTING STERN ROLLERS IN ANCHOR PLANTING TENDERS [76] Inventor: Mehmet D. Korkut, 3848 Veterans Hwy., New Orleans, La. 70002 [22] Filed: June 27, I973 [21] Appl. No.: 374,207

[52] US Cl ..114/0.5 R, 61/723, 114/206 A [51] Int. Cl B63b 21/22 [58] Field of Search 114/0.5 R, 43.5, 235 R,

114/235 A, 206 A, 70; 254/1343 SC; 6l/72.3

[56] References Cited UNITED STATES PATENTS 3,205,845 9/1965 Slingelandt l14/O.5 A 3,280,777 10/1966 Matzer 114/70 3,438,213 4/1969 Broussard et al. 61/723 3,734,046 5/1973 Schmidt et al l14/43.5 X

Primary Examiner-Trygve M. Blix Assistant ExaminerGregory W. OConnor Attorney, Agent, or FirmJames B. Lake, Jr.

[ ABSTRACT An anchoring tender has a centrally indented stern and a center stern member adapted to fit and be pivotally fastened by a forward end in said indented stern for pivoting an after free end downward from an inoperative and non-drag position within said tender. A stern roller is mounted for rotation on said free end of the longitudinal member, the axis of rotation of the stern roller being transverse the indented stern and the stern roller being out of the water when the longitudinal member is in inoperative and non-drag position, and in the water and below center of gravity of tender when transverse member is pivoted downward to an operative position. The perimeter of the stern roller is a continuation of a channelway in said stern member and together define approximately an end of a catenary in a vertical plane formed by an anchor line led out by said tender from a rig to be anchored. Lowering the stern roller below the center of gravity of the tender stabilizes its stern under load of anchoring tackle, and the application of power in approximate line of catenary reduces necessary power by more than half, and diameter of stem roller by half.

2 Claims, 4 Drawing Figures PATENIED FEB I 8 I975 SHEET 1 BF 2 FIG. 2

PATENTH] FEB] 8|975 sum 2 or 2 FIG. 3

APPARATUS FOR MOUNTING STERN ROLLERS IN ANCHOR PLANTING TENDERS The invention relates to tenders for planting and raising anchors and more particularly to apparatus for and method of mounting stern rollers on said tenders for safe handling of ground tackle.

In anchoring large semi-submersible oil rigs, in connection with which the invention is described, anchors of more than 50 tons must be led out and planted some distance from the rig. Lines for such anchors in necessary lengths are also relatively heavy and must be led out from the rig. With such an anchor secured in the stern of the tender and with the led-out anchor line assuming a catenary curve, the applied mass to the stern of the tender, heretofore all above its center of gravity, tends and frequently does capsize the tender, shooting its stern to one side or the other as it heels over.

At first the anchors were placed against an A frame mounted in the stern on the tenders deck, and the anchor line led over a roller mmounted for rotation at the apex of the A frame, but the additional leverage multiplying the weight of anchor and line was so disastrous in capsizing tenders that the roller was mounted on deck without the A frame but yet above the tenders center of gravity. A roller of about seven feet in diameter was required to reduce the sharp angle made by the anchor line as it went over the roller to a winch that needed 200,000 to 250,000 lbs. pull to handle the line and/or the anchor, and the tenders stern remained unstable.

It is an object of the invention to stabilize a tenders stern while planting or raising an anchor from the stern thereof.

Another object of the invention is to reduce by at least half the size of a stern roller and the actuating power therefor while handling anchors and lines of the same size.

Other objects and a more complete understanding of the invention may be had by referring to the following description, claims and drawings, in which:

FIG. 1 is a side view of the invention in use,

FIG. 2 is an enlarged side view of a preferred specie of the invention shown mounted on a stern of a tender,

FIG. 3 is an enlarged plan view of the matter of FIG. 2, and

FIG. 4 is a side view of a second specie of the inventron.

Referring to FIGS. 1-3, a preferred specie of the invention comprises in combination with tender 12 with an indentation 14 in its stem 16, a center stern member 18 adapted to fit indentation 14 and transversely pivoted by an end 19 therein. A roller 20 is rotatably mounted at the free end 21 of section 18 for rotation around an axis 22 parallel to transverse axis 24 of pivoted section 18. When stern section 18 is pivoted fully into hull alignment and inoperative, axis 22 and roller 20 are above axis 24, and when stern member 18 is pivoted downward into operative position and out of hull alignment, axis 22 is below axis 24 and below the center of gravity of the tender.

Center stern member 18 comprises and upper surface 26 and a lower surface 28. A center channelway 30 is defined and said upper surface 26 to serve as an anchor line lead and support between roller 20 and a power winch 32. Channelway 30 in longitudinal vertical cross-section defines a modified composite end of a variable catenary curve. Such a curve is defined by anchor line 34 as it hangs between a rig 36 and anchoring tender 12, and it is important in reducing power and friction for channelway 30 and perimeter of roller 20 to conform closely to a catenary curve end.

An hydraulic cylinder 38 is mounted in the tender l2 and adjacent upper surface 26 of pivoted end 40 of member 18, and is adapted to pivot member 18 about its pivot axis 24 that is adjacent its lower surface 28.

In use anchor line 34 is payed out between rig 36 and tender 12, the line passing through the channelway 30 and over roller 20 which are positioned by the load and cylinder 38 approximately as a catenary end. As the tender movers away from the rig member 18 is pivoted about its axis 24 with cylinder 38 exercising a drag just sufficient to keep roller 20 in contact with the anchor line. When preparing to drop anchor, the line 34 is stopped between roller and winch 32 by any convenient and well-known means, and the end shackled to an anchor with a lighter buoy line (not shown) to mark position of anchor and serve as a retrieving line when the anchor is to be raised. The anchor is lowered by means of the roller, winch and buoy line. The anchor is recovered in reverse procedure.

Referring to FIG. 4, a second specie of the invention comprises a stern roller 42 mounted in a transom 44 of a tender 46. The roller is adapted to rotate on a transverse axis 48 on or below center of gravity 50 of the tender. Transom 44 is raked to the roller 42 for reducing the angle of pull of the winch.

In the first specie, a tenders stem is stabilized by p0- sitioning the entire roller below the center of gravity of the tender and thereby obtaining a stabilizing leverage and moments of force.

In the second specie, the axis of rotation of the roller is on or slightly below the center of gravity of the tender and thereby practically centering gr und tackle weight and eliminating leverage and moments of force.

What is claimed is:

1. In a tender for leading out anchor lines and anchors in mooring semi-submersible drilling rigs and such like marine platforms, said tender having a center of gravity, a longitudinal centerline, and an indented stern symetrically arranged on said centerline; a ramp pivoted symmetrically with respect to said centerline in said indented stem with oppositely disposed free aft and forward fixed ends, said ramp being swingable' between an inoperable in-hull-alignment position with said free end above said center of gravity, and an operable position with said free end below said center of gravity; and a stern roller rotatably mounted on said ramp at said free end with its axis of rotation horizontal and normal to said centerline, said stern roller being scored with a circumferential center channel symmetrically positioned with respect to said longitudinal centerline for receiving and guiding anchor lines passing thereover in leading out such and anchors to position of planting from a said drilling rig with said ramp in operable position whereby the weight of said line hanging in a catenary therebetween is supported by said tender below its center of gravity and acts to stabilize said tender in its movements.

2. In a tender as described in claim 1 wherein the upper surface of said ramp is curved in continuation of a composite of possible catenary curves of said suspended anchor line, the receiving surface of said center channel of the stern roller also lying on said continuous catenary line for a reduction in friction between the passage of lines over said roller and ramp. 

1. In a tender for leading out anchor lines and anchors in mooring semi-submersible drilling rigs and such like marine platforms, said tender having a center of gravity, a longitudinal centerline, and an indented stern symetrically arranged on said centerline; a ramp pivoted symmetrically with respect to said centerline in said indented stern with oppositely disposed free aft and forward fixed ends, said ramp being swingable between an inoperable in-hull-alignment position with said free end above said center of gravity, and an operable position with said free end below said center of gravity; and a stern roller rotatably mounted on said ramp at said free end with its axis of rotation horizontal and normal to said centerline, said stern roller being scored with a circumferential center channel symmetrically positioned with respect to said longitudinal centerline for receiving and guiding anchor lines passing thereover in leading out such and anChors to position of planting from a said drilling rig with said ramp in operable position whereby the weight of said line hanging in a catenary therebetween is supported by said tender below its center of gravity and acts to stabilize said tender in its movements.
 2. In a tender as described in claim 1 wherein the upper surface of said ramp is curved in continuation of a composite of possible catenary curves of said suspended anchor line, the receiving surface of said center channel of the stern roller also lying on said continuous catenary line for a reduction in friction between the passage of lines over said roller and ramp. 